offers the SeaChanger Color Engine that utilizes gradient dichroic disks to control color. The unit is mounted in between the lamp assembly and optics and is controlled via DMX512. Great American Market (GAM) offers a special effects unit, the SX4, that is mounted inside a Source Four in a similar manner to the Seachanger Color Engine and offers a large selection of drop-in accessories that range from gobo-changers to overlapping looping gobos. Several manufacturers of HMI sources, such as Kobold, provide lighting fixtures that provide "daylight balanced" light through the Source 4 without the use of gels. This is accomplished by replacing the lamp assembly on the back of the Source 4 with an HMI lamp head. Other Source Four products In 1995, ETC introduced the Source Four PAR which is meant to replace traditional PAR cans. It uses the HPL lamp, and has interchangeable lenses. In 1999, ETC introduced the Source Four PARNel as an alternative to Fresnel lanterns. In 2002, ETC introduced the Source Four MultiPAR as an alternative to striplights. In 2004, ETC introduced the Source Four Revolution, ETC's first moving fixture. The Revolution was awarded both the EDDY and ABTT awards. The Revolution has the same filament structure as famous HPL Source Four lamp, as opposed to most other moving lights, which use arc lamps, or, more recently, LEDs. Also, the Revolution uses a gel string color scroller instead of the typical color wheel, thus allowing lighting designers to use familiar gel choices. In 2011, ETC introduced the Source Four Fresnel, which is a fresnel light that uses the HPL lamp. References Stage lighting instruments